How to detect current audio device volume

Question

I want to detect the current volume for the default audio recording device of the current computer. Is there any API to use or solutions?

I am writing an audio recorder and I want to let the user know the current volume for the default audio recording device before recording, so that we can avoid a no-audio-recorded issue (e.g. end user has audio recording device muted).

If the result could be retrieved in the format of a percentage value (i.e. 0% means mute, and 100% means max volume), it would be great!

I am using VSTS 2008 + C# + .Net 3.5 to write a Windows Forms application.

Answer 1

The way to do this is to open the default WaveIn device using WaveInOpen and that will get you a waveIn handle. Then you can use the mixer... APIs to select the associated mixer line.

This will be a destination line, and will have some controls (often a mute and a volume). You may be able to set these. However, this is where it gets a little complicated. There are also multiple "sources" associated with a destination (e.g. Microphone, Line In etc). These too can have volume and mute and other custom controls. You may need to experiment a little to find the control you really want to change. I have found it hard to come up with code that works reliably on both Vista and XP (it may actually be to do with your sound card drivers).

I have written managed wrappers for all these functions in NAudio which will get you part of the way. This is roughly what you want to do:

MixerLine mixerLine;
if (waveInHandle != IntPtr.Zero)
{
    mixerLine = new MixerLine(waveInHandle, 0, MixerFlags.WaveInHandle);
}
else
{
    mixerLine = new MixerLine((IntPtr)waveInDeviceNumber, 0, MixerFlags.WaveIn);
}

foreach (MixerControl control in mixerLine.Controls)
{
    if (control.ControlType == MixerControlType.Volume)
    {
        // this is the volume control of the "destination"
        UnsignedMixerControl volumeControl = (UnsignedMixerControl)control;
        Debug.WriteLine(volumeControl.Percent.ToString());
    }      
}

// to examine the volume controls of the "sources":
if (source.ComponentType == MixerLineComponentType.SourceMicrophone)
{
    foreach (MixerControl control in source.Controls)
    {
        if (control.ControlType == MixerControlType.Volume)
        {
            // this might be the one you want to set
        }
    }
}

Answer 2

For capture devices, the mixer volume and the endpoint volume both reflect the volume of the actual capture hardware (this lets apps that use AGC work correctly without modification).